Magnetic tape cassette

ABSTRACT

The magnetic tape (8) is guided in the conventional manner from a first reel hub over a deflection pulley to the recording or playback zone and from there over a further deflection pulley (21) to the second reel hub. In each cassette part between the recording or playback zone and the reel hub, a U-shaped tape clamp (25) is placed onto the magnetic tape (8). A slide (74) is provided with two spaced stops (81, 82) for the tape clamp (25), which stops, in one position of the slide (74), firmly hold the tape clamp, without hindering the magnetic tape (8) (normal operation). In the other position of the slide (74), the tape clamp (25) runs with the magnetic tape (8) onto the reel hub in the case of forward-winding or, in the case of re-winding, the tape clamp runs into the gap formed by a fixed projection (73) on the housing and a surface (83) of the slide (74), where it is pressed together and stops the magnetic tape (8) (memory operation). By actuating the slide (74) at any desired selected point of the magnetic tape (8) and after subsequent forward-winding the later re-winding can be automatically stopped at the selected point.

The invention relates to a magnetic tape cassette according to thepreamble of Patent claim 1.

When known magnetic tape cassettes of this type are used in conjunctionwith appropriate recording and playback equipment, it is often desiredto play back a certain section of the magnetic tape, containing arecording, several times in succession. This is the case particularlyduring the use of magnetic tape cassettes which contain language lessonswhich are to be impressed on the memory sectionally by repeatedplayback. In this mode of use, it is thus necessary, after theparticular section of magnetic tape has been played back, to wind themagnetic tape back to the start of the section.

In order to avoid a laborious and time-consuming search, by alternatere-wind and playback, for rapidly locating the start of the section ofmagnetic tape which is to be played back repeatedly, recording andplayback equipment is known which has a so-called "memory" device. Theseare devices which, for example in conjunction with a tape-length counteror with means for applying control signals to the magnetic tape, stopthe transport of the magnetic tape during re-wind at a previously setpoint of the magnetic tape, compare, for example, U.S. Pat. No.3,601,555.

From U.S. Pat. No. 3,810,246, it is known to provide one or both edgesof the magnetic tape with visually discernible markings which, forexample, designate pauses between recorded program sections and whichare visible through the window of the magnetic tape cassette. Moreover,it is known from British Pat. No. 1,040,262, to provide the magnetictape, at certain points, with permanent thickenings, for example stripswhich are glued on, which can be sensed by means of an instrument formeasuring the tape thickness, for example a roll, in order to switch theequipment over when such a thickening is detected.

It is the object of the present invention to provide a device for theautomatic location of a defined point, which can be selected as desiredand can be shifted, on the magnetic tape when the latter is re-wound,which device is independent of the design of the recording and playbackequipment used. It is a further object of the invention to constructsuch a device in a magnetic tape cassette in such a way that theoperation of the device is simple and reliable, that the magnetic tapecassette meets the existing standards with respect to its dimensions andoperational specifications and contains a conventional unchangedmagnetic tape, and the production costs of the magnetic tape cassettesubstantially correspond to those of hitherto known and customarymagnetic tape cassettes.

To achieve this object, the magnetic tape cassette according to theinvention has the features indicated in the characterising clause ofPatent claim 1.

According to one embodiment of the invention, the stops can be rigidlyjoined to the shells, each control element being a control slide whichcomprises a grip portion, projecting outwards through an aperture in theshell concerned, and two cheeks which project into the interior of thehousing and between which the magnetic tape runs, it being possible tomove the magnetic tape out of the zone of the stops by actuating thecontrol slide.

Conversely, each control element can either be a control lever rotatablymounted in the shells or a control slide displaceably mounted betweenthe shells, which lever or slide comprises the two stops for the tapeclamp, a grip zone which is accessible from outside the housing, and asurface zone, arranged opposite the guide element for the magnetic tape,for clamping in and compressing the tape clamp.

Illustrative embodiments of the magnetic tape cassette according to theinvention and its mode of functioning are explained in the followingtext by reference to the drawings in which:

FIG. 1 shows a plan view of a magnetic tape cassette in a firstembodiment,

FIG. 2 shows a plan view of the interior of the magnetic tape cassetteof FIG. 1,

FIG. 3 shows a perspective view, on a larger scale, of a tape clamp ofthe magnetic tape cassette of FIGS. 1 and 2,

FIG. 4 shows a perspective view, on a larger scale, of a control side ofthe magnetic tape cassette of FIGS. 1 and 2,

FIG. 5 shows a plan view of a part of a magnetic tape cassette in asecond embodiment, in an operating position which allows the magnetictape to run through,

FIG. 6 shows a plan view, corresponding to FIG. 5, in an operatingposition which effects a stop of the tape,

FIG. 7 shows a plan view of a part of a magnetic tape cassette in athird embodiment, in an operating position which allows the magnetictape to run through,

FIG. 8 shows a plan view, corresponding to FIG. 7, in an operatingposition whifh effects a stop of the tape, and

FIG. 9 shows a lateral view of a slide of the embodiment according toFIGS. 7 and 8.

According to FIGS. 1 and 2, the housing of the present magnetic tapecassette has, in a known manner, an upper shell 1 and a lower shell 2which are provided with side walls 3 and are mutually joined by means ofscrews 4, a part of the side walls 3 having raised inner edges 3a forreinforcement. In a manner likewise known, the two shells 1 and 2 of thehousing are provided with a recording and playback zone 5 which is notexplained in more detail and in which a magnetic tape 8, wound up on tworeel hubs 6 and 7, is pressed against the heads (combined sound head,erasing head) of the recording and playback equipment and is moved pastthese. The shells 1 and 2 are also provided with a window 9 which isdivided by a bridge 9a and through which the tape reels 10 and 11arranged on the reel hubs 6, 7 can be seen. The bridge 9a divides thewindow 9 into two sight zones in such a way that, in each sight zone,always only the outer rim of the smaller reel of magnetic tape wound upon the reel hubs 6 and 7 is visible. This not only facilitates readingoff the available tape or the tape which has already been played back,on a scale 9b marked on the sight zones of the window 9, but it alsomakes it possible to make the scale 9b approximately linear and toprovide it with a calibration in minutes.

As distinct from the known magnetic tape cassettes, the present magnetictape cassette according to FIG. 1 has, in its upper shell 1 and, asindicated, also in the lower shell 2, a rectangular aperture 12 or 13through which projects a grip portion 14 of a control slide 15 or 16,respectively, arranged in the interior of the housing below the aperture12, only one slide 15 being shown in FIG. 1, but both slides 15, 16being visible in different positions in FIG. 2. The apertures 12 and 13are arranged in that corner of the shell 1 or 2 respectively, close tothe recording or playback zone 5, through which the magnetic tape ismoved in the interior of the housing during playback from the said zone5 to the corresponding reel hub 7 or 6. The grip portion 14 does notproject from the aperture 12 or 13 beyond the height of the shell 1 or2, in the recording and playback zone 5, so that the insertion and theoperation of the present magnetic tape cassette in any customaryequipment is not impeded in any way by the control slides of the twoshells 1, 2. The functioning of the control slides will be explainedbelow.

As can be seen from FIG. 2, one rotatable guide and reversing pulley 19or 20 for the magnetic tape 8 is arranged on each side of the recordingor playback zone 5, in a manner known per se. At a defined spacing fromthe pulleys 19, 20, a further rotatable guide pulley 21 or 22 for themagnetic tape 8 is arranged, from where the magnetic tape 8 passes tothe appropriate tape reel 10 and 11. Close to the respective pulleys,two stops 23 and 24 which are moulded as projections of the lower shell2 and which are formed, for example, as cams are arranged between thetwo pairs of pulleys 19, 21 or 20, 22 respectively. The distance betweenthe two stops 23 or 24 in the direction of the magnetic tape is slightlylarger than the width of tape clamps 25 and 26, one of which is placedin each case onto the magnetic tape section between the first pulleys 19and 20 and the associated tape reels 10 and 11.

In FIG. 3, the tape clamps 25, 26 are shown greatly enlarged. Theyconsist of thin-walled plastic and have a U-shaped cross-section. Thewall thickness is, for example, 0.25 mm, the overall thickness of themoulded tape clamp is 0.8 mm and the width is, for example, 5 mm. Thelength of the tape clamp shown corresponds to the width of the magnetictape 8. This shows that the tape clamp 25, 26 can be placed loosely ontothe magnetic tape 8 and can be displaced on the latter, or the movingmagnetic tape 8 can be passed through, virtually without friction,between the two arms of the tape clamp 25, 26, as long as the arms arenot compressed. Due to the small thickness of the tape clamps 25, 26, itwill also be understood that these cannot adversely affect the tapereels 10, 11, when the tape clamps 25, 26 together with the magnetictape 8 are wound up on the reel hubs 6, 7 or unwound from the latter.The width of the tape clamps 25, 26 and the distances between the stops23, 24 are matched in such a way that the tape clamps placed onto themagnetic tape 8 can be inserted with play between the respective stops23 or 24, as shown in FIG. 2 for the stops 24 and the tape clamp 26.

As can be seen from FIG. 2, the control slides 15, 16, alreadymentioned, are arranged between the stops 23 or 24 and are displaceable,approximately diagonally with respect to the shells 1, 2, within theaperture 12 or 13 (FIG. 1) by means of the grip portion 14. In FIG. 2,the control slide 15 is shown in the outer terminal position and thecontrol slide 16 is shown in the inner terminal position. The controlslide 15 is drawn with the grip portion 14 cut off.

In FIG. 4, the control slide 15 is shown in perspective and greatlyenlarged. It has two sliding parts 29 and 30 which bear against theinner wall of the shell 1 and between which the grip portion 14 isarranged. Moreover, it is provided with an outer cheek 31 and an innercheek 32. The cheeks 31, 32, between which the magnetic tape 8 is passedthrough (FIG. 2), have rounded inner surfaces. The control slide 16 isdesigned in the same way as the control slide 15 shown.

In normal recording or playback operation, the two control slides 15, 16are shifted in the direction toward the centre of the cassette into theterminal position, as shown in FIG. 2 for the left-hand control slide16. As a result, the moving magnetic tape 8 glides over the stops 24.When the tape clamp 26 arranged on the tape reel 11, during a movementof the magnetic tape 8 in the direction from the tape reel 11 to thetape reel 10, then passes over the pulley 22 to the stops 24, it iscaptured by the two stops 24, the outer cheek 31 of the control slide16, which gently presses on the magnetic tape 8 or the tape clamp 26,preventing the tape clamp 26 from jumping out of the grip of the stops24 when the tape runs fast. The tape clamp 26 remains in this capturedposition as long as the control slide 16 is in the inward-displacedposition. Since the magnetic tape 8 is loosely guided in the tape clamp26, it can be moved virtually unhindered in the playback or forwarddirection or in the re-wind direction.

This applies analogously to the control slide 15, if it is in theinward-displaced position. If, however, the control slide 15 isdisplaced into the outer terminal position, as shown in FIG. 2, itsinner cheek 32 lifts the magnetic tape 8, and hence also the tape clamp25 placed thereon, off the stops 23. When the magnetic tape 8 is thenmoved in the direction from the tape reel 10 to the tape reel 11(re-wind), the tape clamp 25 reaches the position shown in FIG. 2, inwhich it is clamped in between the pulley 19 of the front side wall 3and a boss 35 on the housing for the screw fixing of the shell 1 (FIG.1). On the one hand, this prevents a further transport of the tape clamp25 into the recording or playback zone 5. On the other hand, the arms ofthe tape clamp 25 are compressed by the clamping action, so that themagnetic tape is instantly clamped tight and stopped by the arms of thetape clamp 25 since, with increasing friction, the traction forceexerted by the magnetic tape on the tape clamp increases and in turn hasthe effect that the tape clamp jams more tightly between the pulley 19and the side wall 3 and, with its arms, presses on the magnetic tape. Asin the case of the tape stop at the end of the magnetic tape 8, thelatter thus immediately comes to a standstill, whereby the drivemechanism for the magnetic tape 8 is switched off, at least in part ofthe customary equipment.

As can be seen from FIG. 2, one end of the tape clamp 25 bears on itsone side against the pulley 19 and the same end bears on the other sideagainst the lower side wall 3, whilst its other end bears on itslast-mentioned side against the boss 35 on the housing. This results inflip-clamping which can be released immediately by a very slight pull ofthe tape in the opposite direction, without the tape clamp 25 stickingin the position shown. Rather, when the magnetic tape 8 runs forwardagain, the clamp is pulled over the pulleys 19, 21 and wound up on thetape reel 10. During a subsequent re-winding of the magnetic tape 8, theclamp then reaches again the position shown in FIG. 2, between thepulley 19, the side wall 3 and the boss 35 on the housing, and stops themagnetic tape 8; during these steps, the position of the tape clamp 25relative to the magnetic tape 8 has not changed, or has at mostinsignificantly changed due to slip.

The use of the present magnetic tape cassette thus involves only thefollowing steps:

(1) Insertion of the cassette into the equipment in the conventionalmanner, for example in such a way that the side shown in FIG. 1 is theupward-facing side "B" which is to be played back. The two controlslides 15 and 16 (apertures 12 and 13 in FIG. 1) are in this case to beshifted into the inner position if normal operation with unhinderedplayback, forward-wind and re-wind is desired.

(2) Stopping of the magnetic tape at that point which is later to beautomatically located by running back the magnetic tape.

(3) Shifting the control slide 15 into the outer position, which can beaccomplished by merely opening the cassette compartment lid of theequipment, without taking the cassette out of the equipment. During eachre-wind of the magnetic tape, effected after forward-wind, playback orfast forward-wind, the tape is stopped automatically at that point atwhich the tape was in the recording and playback zone 5 of the cassette,when the control slide 15 was shifted into its outer position.

When the magnetic tape cassette is in the inverted position in theequipment, it is of course also possible to automatically locate anypoint preselected by means of the control slide 16 on the other track ofthe magnetic tape. Moreover, it is possible, in the same, non-invertedposition of the cassette in the equipment, also to control the movementof the magnetic tape correspondingly in the forward direction, that isto say to let the magnetic tape run forward up to a defined point, atwhich the movement is automatically stopped. For this purpose, the othercontrol slide 16 is shifted at the selected point from its normal innerposition into the outer position. When equipment is used which isequipped for the so-called "auto reverse" operation, automatic andrepeated playback of both tracks of the magnetic tape between any twodesired points can be obtained in this manner.

In principle it would be conceivable to design and arrange the controlslides 15 and 16 in such a way that either can be actuated from bothsides of the cassette or on the front end face of the cassette.

Because, in repeated search operation of the present magnetic tapecassette, that is to say with repeated playback of a short section ofmagnetic tape, rewinding to the start of this section, and so on, thereis a risk of the magnetic tape not being properly wound up on thewinding and stock reel and causing a so-called "doming" or a so-called"tape pile-up" due to the formation of a loop in the tape, the measuresexplained below can be envisaged.

In the magnetic tape cassette shown in FIG. 2, a foil 40 is placed, in amanner known per se, between each of the shells 1, 2 of the housing andthe adjacent tape reels 10, 11. The foil 40 consisting, for example, oftransparent PVC has a width which is less than that of known foils and,in the direction of the width, it extends only over the reel hubs 6 and7. The foil 40 is provided with raised portions 42, for example bentfolds, which are radial with respect to the circular cut-outs 41, andwith raised portions 43 which extend rather in the longitudinaldirection and which have the effect that the foil 40, along these raisedportions, presses resiliently on the reel hubs 6, 7 and the tape reels10, 11. The longitudinal elevations 43 thus serve to hold the magnetictape 8, which runs onto the tape reels 10, 11, always in the centre ofthe reel hubs 6, 7 and to prevent the so-called "doming" on the tapereels. The radial elevations 42 which essentially act only on the reelhubs 6, 7 and the innermost part of the tape reels 10, 11, hold the reelhubs 6, 7 in the centre between the shells 1, 2. In addition, the raisedportions 42 only act on the innermost part of the tape reels 10, 11, inorder to obtain, even in the case of a small tape reel, a sufficientlylarge frictional force which brakes the tape reel which is running down,when fast tape-winding is stopped. In this way, the formation of a tapeloop is avoided, which could lead to difficulties when the capstan ofthe equipment is switched on again ("tape pile-up"). An additionaleffect of the foil 40 which has been described and of further meanswhich will be explained below is that, after the cassette has been takenout of the equipment, the tendency of the tape reels to unwindautomatically due to shocks and hence to cause a troublesome tape loopis much reduced.

FIG. 2 shows an endless tape 36 which is inserted into the shell 2, isguided around two pins 37, 38 and adheres against the tape reels 10 and11 with appropriate rigidity. The tape 36 which, for example, consistsof paper or plastic has three different functions: firstly, it rubs onthe outsides of the tape reels 10, 11, is set in motion by the latterand thus cleans the magnetic coating of the magnetic tape 8. Secondly,the tape exerts a braking moment on the tape reels 10, 11. Thirdly, thetape 36 makes it easier to see the outer rim of tape reel 10, 11,whichever is the smaller at the time, through one of the two sight zonesof the window 9 of FIG. 1.

The braking action of the tape 36 on the tape reels 10, 11 is greatestwhenever one tape reel is smaller than the other. The tape 36 is thenmoved by the larger tape reel in the direction opposite to the directionof movement of the smaller tape reel, so that the braking action on thesmaller tape reel is reinforced. This not only stops the tape reel fromrunning empty when the magnetic tape 8 is stopped, but it also has abalancing effect on the tape tension during playback: the winding hub isbraked in the case of a small tape reel, when the tension is high,whilst the unwinding hub is driven in the opposite direction in the caseof a small tape reel, when the tension is low.

During search operation of the present magnetic tape cassette, that isto say when playback and return of a relatively short section of themagnetic tape are repeated many times, the measures described,individually or in combination, ensure uniform winding-up of themagnetic tape on the reel hubs and optimum tape tension in bothdirections of movement of the magnetic tape for any particular diametersof the tape reels.

In FIGS. 5 and 6, a further embodiment of the device for effecting astop of the tape at any desired point along the magnetic tape isillustrated. FIGS. 5 and 6 here show a section comprising the bottomright corner of the housing of the magnetic tape cassette of FIG. 2,with the further embodiment on a larger scale. Accordingly, the sidewalls 3 of the lower shell 2 of the housing, and the two rotatable guideand reversing pulleys 19, 21, over which the magnetic tape 8 passes toone of the two tape reels which are not shown here, are visible.

Between the two shells of the housing, of which the lower shell 2 isshown in FIGS. 5 and 6, a lever 56 is arranged which has two leverportions 57 and 58 and is rotatably mounted on a pin 59. The pin 59serves at the same time as a boss on the housing for the screw fixing ofthe other shell on the shell 2, corresponding to the boss 35 on thehousing in FIG. 2. The lever portion 57 is provided with grippingnotches 60 which are situated in a cut-out zone of the two side walls 3and are thus accessible from the outside for turning the lever 56.Additionally, the lever portion has two projections 61 and 62 or,conversely, a corresponding recess. Via a plate-type connecting piece63, the lever portion 57 merges into the lever portion 58. The latter isprovided on its end with pins 64 which are mounted in slots 65 of thelower shell 2 and also of the upper shell which is not shown. The lever56 can also be turned by means of these pins 64 which are accessible onthe outsides of the two shells.

In one operating position of the lever 56, according to FIG. 5, themagnetic tape 8 runs over the two projections 61, 62 of the leverportion 57 and through a gap between the guide pulley 19 and a surface57' of the lever portion 57. When, during the re-winding of the magnetictape 8, that is to say during a movement of the magnetic tape 8 from theguide pulley 21 to the guide pulley 19, the tape clamp 25 placed on thetape passes from the tape reel which is not shown to the lever portion57, it is arrested by the projection 61 which acts as a stop. Since thetape clamp 25 lies loosely on the magnetic tape 8, however, the magnetictape 8 continues to run on virtually unhindered. In the oppositedirection of running of the magnetic tape 8, the tape clamp 25 isretained by the other projection 62 of the lever portion 57, withouthindering the run of the magnetic tape 8.

When the lever 56 is then brought, by turning, into the operatingposition shown in FIG. 6, the projections 61 and 62 are removed from thepath of the magnetic tape 8. When the magnetic tape 8 is then moved inthe forward direction from the pulley 19 to the pulley 21 and to thetape reel after the latter, for example when a recording is played back,the tape clamp 25 is no longer retained by the projection 62 and,instead, it moves with the magnetic tape 8 to the appropriate tape reel.When the magnetic tape 8 is subsequently rewound, the tape clamp 25reaches the guide pulley 21 (FIG. 6) at a certain point in time in thesame position relative to the magnetic tape and then reaches the zonebetween the pulleys 21 and 19. Since the gap between the pulley 19 andthe surface 57' of the lever portion 57, lying opposite, is only of asize just sufficient for the magnetic tape 8 to pass through unimpeded,that is to say it has a width of about 1/10 mm, the tape clamp 25strikes at the pulley 19 and the surface 57' and is compressed becauseof the tapering of the particular surface portions, so that the magnetictape 8 is instantly clamped tight and stopped by the arms of the tapeclamp 25, as has already been described by reference to FIG. 2. Thus,the re-winding of the magnetic tape 8 ends at the point at which theprojections 61, 62 were removed from the path of the magnetic tape 8 byturning the lever 56. In other words, a desired starting point of asection of magnetic tape has been located during re-winding withoutfurther action. When the magnetic tape 8 runs forward again, the tapeclamp 25 is readily released from the guide pulley 19 and the surface57' of the lever portion 57, so that the tape clamp 25 retains itsposition relative to the magnetic tape 8 for as long as the lever 56remains in the position of FIG. 6.

Of course, the other bottom corner of the cassette housing according toFIG. 2 is also provided with an identical lever 56, so that controlledstopping of the tape can be achieved also with an inturned cassette orin the forward-winding direction of the magnetic tape.

A third embodiment of the device for effecting a stop of the tape at anydesired point along the magnetic tape is illustrated in FIGS. 7 and 8,and specifically in the same part view of the magnetic tape cassette asin FIGS. 5 and 6. Accordingly, the side walls 3 of the lower shell 2 ofthe housing are again visible, as is one guide and reversing pulley 21which, on the illustrated side of the magnetic tape cassette, is theonly rotatable pulley. Further guiding and a slight deflection of themagnetic tape 8 are effected by a rounded edge 71 of aninward-projecting rib 72 which is moulded to the lower shell 2 of thehousing. On the opposite side, relative to the magnetic tape 8, anddisplaced by a short distance away from the edge 72 in the direction ofthe pulley 21, the lower side wall 3 is provided with a roundedprojection 73. The edge 71 and the projection 73 thus form a gap throughwhich the magnetic tape 8 passes.

In the space between the rib 72 and the pulley 21, a slide 74 isprovided which is additionally shown in FIG. 9 in a side view, from theside which is the lower in FIGS. 7, 8, and on a larger scale.Accordingly, the slide 74 has a central portion 75 and, on each side,one cylindrical pin 76 and 77. The central portion 75 lies between theinner surfaces of the lower shell 2 and the upper shell of the housing,which is not shown in FIGS. 7, 8. The pins 76, 77 are each mounted in aslot in the two shells, only the slot 78 in the lower shell 2 beingvisible in FIGS. 7, 8. Thus, the slide 74 is both displaceable along theslots 78 and rotatable around the longitudinal axis of the pins 76, 77.For further guiding of the slide 74, which will be explained below, theshell 2 has a further moulded-on rib 79 which, together with the rib 72,guides or limits a movement of the slide 74.

According to FIGS. 7 to 9, that side of the slide 74 which faces themagnetic tape 8 is provided with a recess 80 which is bounded by twoprojections 81, 82 and essentially corresponds to the recess with theprojections 61, 62 of the lever portion 57 in FIGS. 5, 6. One projection81 is guided further as a rib-type projection 83 around the adjacentcorner and the adjoining side of the slide 74. The pins 76, 77 are eachprovided with a blind hole 84 and 85 respectively, which makes itpossible to shift the slide 74 in the slots 78 from the outside with theaid of a pointed object, for example a pencil. Finally, a furtherrounded projection 86, the function of which will be explained below, ismoulded to the lower side wall 3 opposite the recess 80 of the slide 74.

It can be seen from FIGS. 7 and 8 that the slide 74, when actuated andmoved out of the position according to FIG. 7, not only executes atranslatory movement along the slot 78 or the two slots but, due to therib 79 which forms a stop for that corner of the slide 74 which is topleft in FIG. 7, also executes a rotary movement until the projection 83of the slide 74 strikes the rib 72 (FIG. 8).

The mode of action of the slide 74 shown is as follows:

As in the preceding illustrative embodiments, the magnetic tape 8 isprovided with a tape clamp 25 which is loosely placed thereon and whichis shown in greater detail in FIG. 3. It may be assumed that the tapeclamp 25 is initially situated on the tape reel which is associated withthe pulley 21 and is not shown in FIGS. 7, 8. With the magnetic tape 8being re-wound, as indicated by an arrow 87, and with the slide 74 inthe position according to FIG. 7, the tape clamp 25 passes over theprojection 82 into the recess 80 of the slide 74 and is retained in therecess 80 by the other projection 81. The magnetic tape 8, however, canmove on virtually unimpeded, since the tape clamp 25 sits loosely on themagnetic tape 8. When the magnetic tape moves again in the playback orforward-winding direction opposite to the arrow 87, the tape clamp 25 istaken along in the recess 80 for a very short distance until it isretained by the projection 82 of the slide 74, this position being shownin broken lines in FIG. 7. As in the case of the above re-winding,however, the magnetic tape 8 can continue to run because of the looseseating of the tape clamp 25. In order to ensure rectilinear running ofthe magnetic tape 8 in the recess 80 of the slide 74 and to prevent thetape clamp 25 from jumping out over the projections 81, 82, the roundedprojection 86 of the lower side wall 3 limits a lateral movement of thetape clamp 25. Thus, with the slide 74 in the position according to FIG.7, the tape runs as usual in both directions, as though the slide 74were not present.

When effective stopping of the tape is then desired at a defined pointof the magnetic tape 8, during re-winding of the magnetic tape, it isfirst ensured that the tape clamp 25 is actually in the recess 80 of theslide 74; if necessary, this can be accomplished by a complete return ofthe magnetic tape 8, with the slide 74 in the position according to FIG.7. At the desired stopping point of the magnetic tape 8, the re-wind orforward movement of the magnetic tape is interrupted, and the slide 74is shifted into its other position according to FIG. 8. When themagnetic tape 8 is moved again in its forward direction opposite to thearrow 87, the tape clamp 25 is taken along by the magnetic tape 8 andpasses over the pulley 21 to the associated tape reel since, as can beseen from FIG. 8, the recess 80 with the projection 82 is no longer inthe straight-line path of the magnetic tape 8 between the edge 71 of therib 72 and the pulley 21.

During a subsequent re-winding of the magnetic tape 8 in the directionof the arrow 87, the tape clamp 25 passes again from the said tape reelinto the range of the slide 74, but it is not retained there, as it waswith the slide 74 in the position according to FIG. 7, by the projection81, since the latter likewise lies outside the path of the magnetic tape8 (FIG. 8). Rather, the leading edge of the tape clamp 25 passes intothe constriction formed, on the one hand, by the rounded projection 73of the lower side wall 3 and, on the other hand, by the rib-typeprojection 83 of the slide 74. As a result, the tape clamp 25 is pressedtogether, jams on the magnetic tape 8 and prevents further running ofthe magnetic tape 8, since the tape clamp 25 is firmly held in the saidconstriction. Thus, automatic stopping of the tape is achieved at thedesired point in re-winding the magnetic tape 8. Since only the frontedge of the tape clamp 25 is compressed and clamped in, the tape clamp25 is immediately released from the said constriction, when the magnetictape 8 subsequently runs in the forward direction, and is taken alongagain by the magnetic tape to the pulley 21 and to the associated tapereel. By renewed re-winding, stopping of the tape can thus be effectedseveral times at the same point of the magnetic tape. If stopping of thetape is to be cancelled, it is only necessary to bring the slide 74 intothe position according to FIG. 7.

Compared with the illustrative embodiments described before, theembodiment according to FIGS. 7 to 9 has the advantage of greatsimplicity and of less stringent demands on the dimensional tolerancesof the parts of the housing and the slide, which effect the clamping-inof the tape clamp 25.

As already mentioned in connection with the lever 56 of FIGS. 5, 6, theother bottom corner of the cassette housing shown in FIG. 2 is alsodesigned in the same way as the corner shown in FIGS. 7, 8.

In order to avoid running out of one tape reel, when the tape isstopped, and a "tape pile-up" which likewise might occur in thisconnection, the measures (foils, braking band) already mentioned for theembodiment of FIGS. 1, 2 or other measures can be envisaged. Forexample, it is possible, in the arrangement of FIGS. 7, 8, to form andarrange a thin braking strip, for example an aluminium strip, asfollows: the strip is placed flat onto the inner surface of the lowershell 2, and it extends along the rib 72 from the slide 74 up to andunderneath the tape reel concerned, the rib 79 being provided with aperforation for the strip. In the zone of the slide 74, the strip has alug which is bent upwards by an angle other than 90°. When the slide 74is then brought into the position according to FIG. 8, the slide presseson this lug, so that the strip tends to stand up along one of itslongitudinal edges. The other longitudinal edge of the strip thuspresses on, and brakes, the tape reel.

I claim:
 1. Magnetic tape cassette, having a housing comprising twoshells which encompass a recording and playback zone and in which tworeel hubs for winding and unwinding the magnetic tape together withguide pulleys are located on each of the two sides of the recording andplayback zone, characterized in that, between the recording or playbackzone (5) and the reel hubs (6, 7), a tape clamp (25, 26) of U-shapedcross-section is placed to embrace the magnetic tape (8), that limitelements (19, 20, 3, 35; 19, 57; 73, 74) opposed to one another for themagnetic tape (8) are provided on both sides of the recording andplayback zone (5), which limit elements, on the one hand, form a passagefor the magnetic tape (8), and, on the other hand, clamp in and compressthe legs of the tape clamps (25, 26) in either direction of movement ofthe magnetic tape thereby to clamp and bind the tape, there being a pairof stops (23, 24; 61, 62; 81, 82) for the tape clamps (25, 26)positioned between the guide and the associated reel hub to stopmovement of the clamp, and that, in the zone between the limit elements(19, 20, 3, 35; 19, 57; 73, 74) and the associated reel hub (6, 7), acontrol element (15, 16; 57; 74) is provided which can be actuated fromoutside the housing to assume either of two operating positions andwhich, in its first operating position, moves the magnetic tape (8) intothe zone of a pair of said stops (23, 24; 61, 62; 81, 82) for the tapeclamps (25, 26) and which, in its second position, keeps the magnetictape (8) away from the stops.
 2. Magnetic tape cassette, having ahousing comprising two shells which encompass a recording and playbackzone and in which two reel hubs for winding and unwinding the magnetictape together with guide pulleys are located on each of the two sides ofthe recording and playback zone, comprising, between the recording orplayback zone (5) and the reel hubs (6, 7) on each side of the housing,a flexible tape clamp (25, 26) of U-shaped cross-section presentingopposed legs is placed on the tape to loosely embrace the magnetic tape(8), a pair of limit elements (19, 35; 19, 57'; 73, 74) opposed to oneanother being provided on both sides of the recording and playback zone(5), which limit elements are so spaced, on the one hand, to formbetween them a passage for free movement of the magnetic tapetherebetween, and, on the other hand, to trap and compress the legs ofthe related tape clamp (25, 26) if presented thereto when it moves withthe tape in either direction of movement of the magnetic tape thereby tocause the tape clamp to clamp and bind the tape, a pair of stops (23,24; 61, 62; 8, 82) for the tape clamp in advance of each associated reelhub normally to capture between them and thereby stop movement of theclamp so that the tape normally travels alone without a clamp, ashiftable tape control element (15, 16; 57; 74) actuatable from outsidethe housing to assume either of two operating positions and which, inits first operating position, moves the magnetic tape into the zone of apair of said stops (23, 24; 61, 62; 81, 82), and which, in its secondposition, shifts the magnetic tape away from the stops thereby todisplace the clamp from the stops so the clamp will travel with the tapeand become trapped as aforesaid thereby stopping the tape.
 3. Magnetictape cassette according to claim 2, characterised in that, on both sidesof the recording or playback zone (5), one of the limit elements is aguide pulley (19, 20) for the magnetic tape (8).
 4. Magnetic tapecassette according to claim 3, characterised in that the other limitelement in each case is a fixed part (3, 35) of the housing.
 5. Magnetictape cassette according to claim 3, characterised in that the otherlimit element in each case is formed by a surface (57') of the limitelement (57).
 6. Magnetic tape cassette according to claim 2,characterised in that, on both sides of the recording or playback zone(5), one of the limit elements is a fixed part (73) of the housing andthe other limit element in each case is formed by a surface (83) of thecontrol element (74).
 7. Magnetic tape cassette according to claim 2,characterised in that the stops consist of two cams (23, 24; 61, 62; 81,82) which are spaced apart firmly to hold the tape clamp (25, 26), inthe first position of the control element (15, 16; 57; 74), so thatmagnetic tape alone (8) glides over the cams (23, 24; 61, 62; 81, 82).8. Magnetic tape cassette according to claim 2 or 7, characterised inthat there are stops (23, 24) rigidly joined to the shells (1, 2) andthat each control element is a control slide (15, 16) which comprises agrip portion (14), projecting outward through an aperture (12, 13) inthe appropriate shell (1, 2), and two cheeks (31, 32) which project intothe interior of the housing and between which the magnetic tape (8)runs.
 9. Magnetic tape cassette according to claim 1 or 7, characterizedin that each control element is a control lever (57) which is rotatablymounted in the shells (1,2) and which comprises a grip zone (60,64)which is accessible from outside the housing, therebeing two stops(61,62) for the tape clamp (25), and a surface zone (57'), lyingopposite one limit element (19), for pressing together the tape clamplegs (25).
 10. Magnetic tape cassette according to claim 1 or 7,characterized in that each control element is a control slide (74) whichis mounted in the shells (1,2) and which comprises a grip zone (76,77)which is accessible from outside the housing, therebeing two stops(81,82) for the tape clamp (25), and a surface zone (83), lying oppositeone limit element (73) at least in the second position of the controlslide (74), for compressing together the tape clamp (25).